During submarine cable laying or recovery operations, it is conventional practice to utilise a cable engine which pays out the cable or recovers the cable by gripping the cable between pairs of opposed tired wheels. Several pairs of such wheels are arranged to grip the cable one behind the other and are resiliently biased towards each other to grip the cable. When a repeater housing approaches, they can move apart to accommodate the larger diameter of the repeater housing.
During laying and recovery operations it is sometimes necessary to hold the cable while repairs or jointing to the cable are carried out and a cable stopper is used for this purpose.
Conventionally the cable stopper used comprises several helically-preformed wires which are snapped over the cable and the eye of the stopper is tied by a rope to a fixture on board the ship.
Whilst this known form of cable stopper is successful for short periods, over longer periods it can cause damage to the cable and this could well be the case if for example laying or recovery operations had to be halted during a spell of bad weather.
Furthermore we have found that when laying or recovering cable from extreme depths, damage to the cable can readily occur with this known form of stopper.
It is an object of the present invention to devise an alternative stopper which is convenient to use yet does not cause damage to the cable even at high tensile loads, e.g. greater than 5 tons.
According to the present invention there is provided a cable stopper for use in conjunction with a cable engine which can move the cable in an axial direction, the stopper comprising a plurality of cable clamping elements at spaced locations along the cable axis, each element comprising a pair of cooperating parts having surface grooves dimensioned to form a hole when the parts are urged together, the hole being slightly less in diameter than the cable diameter whereby in use to squeeze the cable and clamp it, wherein the two parts of each said clamping element are mounted on respective supports which can be moved towards and away from the position normally occupied by the cable so as to allow introduction of a cable to the elements and/or to enable passage of a repeater or joint housing past the stopper, and wherein said elements are immovable relative to one another in the direction of the cable axis.
Preferably each block part is mounted for pivotal movement towards and away from a clamping position around the cable to be clamped whereby to make room for the passage of a repeater or joint housing.
Preferably the grooves are provided in respective clamping surfaces each formed in a plastics material supported by a metal backplate.
According to another aspect of the present invention, there is provided a method of temporarily holding a cable on board a ship during laying or recovery operations, comprising applying around the cable at several discrete locations, respective clamping parts, each part having a cooperating groove designed to fit the diameter of the cable such that the diameter of the hole produced by the cooperating grooves is slightly smaller at least in one direction than the diameter of the cable, and applying pressure to the applied parts to thereby clamp the cable at the plurality of locations along the length of the cable.